In early infancy (0 to 24 months), the skull is made up of several separate ‘plates’ of bone, connected by flexible ligaments known as sutures. These sutures are present to allow normal birth and to allow the skull to develop as the infant brain grows. The plates retain some flexibility throughout childhood and as the child ages, the bones fuse together and create a permanent skull shape that cannot change.
However, a skull in infancy is soft enough to be deformed by constant external pressure due to the head being in one position on a firm surface for long periods. Such deformation is referred to as Flat Head Syndrome, or Deformational Plagiocephaly—an umbrella term for several related Head Shape Deformities including Plagiocephaly (an asymmetric flattening to the side of the head), Brachycephaly (a wide head shape with a flat back of the head) and Scaphocephaly or Dolichocephaly (a long thin head shape). The most usual presentation is a brachycephaly with some degree of plagiocephaly, sometimes known as a combination head shape deformity. One way of reducing the severity of such a condition is to provide specially shaped pillows, cushions or mattresses that are designed to minimise the development of a flat head. However, once a baby starts to roll onto its side or to be able to wriggle and move away from the pillow, usually at 3 to 5 months of age, they become minimally effective.
Occasionally, one or more of the sutures between the bone plates is prematurely fused, known as craniosynostosis and this can also cause a head shape deformity. This condition must be corrected by either open scalp or minimally invasive surgery.
In more severe cases of Head Shape Deformity or following surgery to resolve a Craniosynostisis, the infant is fitted with a helmet which gently allows the head shape to grow back towards normality. Typically, the helmets are made from a firm outer shell with a closed cell foam lining. The internal shape of the closed cell foam lining is precisely formed using the following method. A 3D photographic scan is taken of the infant's head shape and this is saved as a computer file. The file is then used to carve a polyurethane foam mould which is modified to a normalised head shape. The modifications can either be done by Computer Aided Design (CAD) or by manually adding plaster or a similar material. The helmet that the infant wears is formed over the modified mould shape and the internal shape comprises contours and recesses that are shaped so as to contact the infant's head in some regions, whilst providing regions where there is a void to allow desired growth.
Although successful in treatment, this type of helmet has several significant drawbacks. The manufacturing process is time consuming and wasteful of materials and energy. There are difficulties in achieving adequate control with large modifications to the mould shape, causing areas of undesirable high pressure and rotation of the helmet. The helmets require frequent internal modifications to allow graduated control and growth. These modifications break the smooth internal surface and cause it to be rough. The closed cell foam liner has high thermal insulating and non-porous characteristics which can cause the infants to sweat excessively, particularly in the initial stages of treatment. There is a high skill level required, both in manufacturing the helmet and in treating the infant. Parents also have a steep learning curve in initiating the treatment for their infant. Some parents report that their infant has difficulties in sleeping with the helmet in place (the helmet must be worn day and night).
It is the aim of this invention to address at least some of the above-mentioned difficulties, and any other difficulties that will be apparent from the description below. It is a further aim of this invention to provide a cost effective, efficacious and hygienic orthosis for correcting head deformities, and an efficient and cost effective method of manufacturing the same.